Changes in Proximate Content of Macroalgae Ulva Sp during Co-culture with Abalone Haliotis squamata in Coastal Waters of West Timor-Indonesia

Abstract

Abalone is luxurious sea food that fetches a very high price. To fulfil increasing market demand, aquaculture is a necessity. Feed is prerequisite for developing aqua culture for this species. In the absence of artificial diets, abalone growers have to depend entirely on macro algae such as Ulva sp harvested from natural population. Abalone are known to consume large amount of algal diet, thus dependence on wild algae could lead to a heavy exploitation of algae population. One of strategies to maintain the supply of Ulva sp is by culturing together with H. squamata in the same area. However, there is no information whether the cultured algae would match the nutritional quality of algae collected from the wild. This research evaluated the proximate composition of Ulva sp growing in two culture systems i.e., cage culture in open sea and recirculating aqua culture system (RAS) in land. The proximate of the cultured Ulva were compared with those freshly collected from the wild. Results showed that protein content differed significantly among the two cultured Ulva and the wild ones (P<0.05). Ulva cultured in RAS contained the highest level of protein (16.89±0.87 % dw), followed by those cultured in cage (11.29±0.31% dw), and the lowest occurred in the wild Ulva. Cultured and wild Ulva had high carbohydrate content ranged from 46.56±5.03 to 49.29±3.5% dw, but ANOVA showed no significant differences among the source of algae (P>0.05). Lipid was a minor component in Ulva with levels ranged from 0.25±0.05 to 0.9±0.31 % dw. There were significant differences in the lipid content among source of algae (P<0.05) with the highest level observed on Ulva grown in RAS, followed in decreasing order by Ulva grown in the cage and the wild ones. This study recommends that abalone growers should culture Ulva because it improves the nutritional quality of the algae and reduces dependence on the wild Ulva that could threaten the natural algal population.